An in-vehicle navigation apparatus holds or stores map data. When a destination is designated, the navigation apparatus calculates a route from a present position to the destination by searching the map data and superimposes the calculated route on a map displayed to thereby perform a route guide.
Incidentally, road states constantly change by accompanying openings or closings of traffics in roads. The navigation apparatus is thus required to update the map data to match with the changes of the road states so that route guides can be performed appropriately. Methods for updating map data include for example, purchasing DVDs having the newest map data, demounting HDDs (Hard Disk Drives) to update the map data at makers or dealers, and downloading the newest map data from center servers. The above methods, however, involve various problems. Purchasing DVDs may involve a cost problem. Demounting and re-mounting HDDs may involve a workload problem. Downloading a large data volume of map data including the newest may involve a time problem.
In contrast, Patent document 1 discloses the following method: capturing a forward image in the travel direction of a vehicle; preparing route course information based on road data indicating connections of roads, e.g., major roads; and superimposing to display the course information on the captured forward image in the travel direction to thereby perform a route guide.
In Patent document 1, however, although the navigation apparatus need not have detail map data, but need to have at least road data simpler than the map data. This requires the navigation apparatus to update the road data for constantly performing an appropriate route guide.    Patent document 1: JP-H10-132598 A